A pore-scale study of foam-microemulsion interaction during low tension gas flooding using microfluidics-Tertiary recovery

The emerging EOR technology of Low-Tension-Gas (LTG) flooding has been proven to be successful for tertiary oil recovery in laboratory scale coreflooding experiments. However, there has not been a detailed study of the pore-scale phenomena which occur during LTG flooding. In the current study, alternate injection of a suitable surfactant formulation and air has been used to simulate the mechanism of LTG flooding in a borosilicate waterwet micromodel. The main phenomenon that was investigated was the interaction between different microemulsion types (Winsor I and III) and foam. Results show that presence of foam facilitates faster and better oil displacement. Microemulsion equilibration time was improved in the presence of foam, due to increased mixing of the liquid phases. Presence of trapped gas helped to divert the flowing surfactant/microemulsion to regions with trapped remaining oil and thus improved oil recovery. For equilibrated Type III microemulsion, completely miscible flooding (or ultralow tension displacement) was observed. For Type I systems, oil-in-water macroemulsions were observed. For equilibrated Type III microemulsion, the presence of foam mainly improved the oil recovery rate. In case of Type III surfactant solution injection, the presence of foam improved both the oil recovery rate and the overall oil recovery. For Type I systems, the presence of foam enabled the transition of oil-in water macroemulsions to water-entrained macroemulsions, thus improving both the oil recovery rate and the overall oil recovery.